This invention relates to a substrate for a magnetic disk and, more particularly, to a substrate for a magnetic disk for high density recording.
Among recent magnetic media (i.e., magnetic disks) for magnetic disk apparatuses, those for high density recording are mainly commonly called thin film magnetic disks having magnetic thin films formed as magnetic recording layer by a plating process, a spattering process or a deposition process.
Such a thin film magnetic disk employs a substrate with the surface thereof polished mechanically to prevent adsorption of magnetic head and magnetic disk to each other. The polishing is usually done by a method called texturing, in which polishing grains are formed circumferentially by a mechanical polishing process.
The process of texturing is an art of forming circumferential polishing grains on the substrate surface. In this art, the surface state can be controlled with conditions of the abrasive grain and the process.
In the prior art magnetic disk, polishing grains are formed concentrically on the substrate surface. However, the repetition of the operation of contact start and stop (CSS) between the magnetic head and magnetic disk leads to an increase of the frequency of adsorption of the magnetic head to the magnetic disk. To decrease this adsorption, the direction of the polishing grains is randomized by slightly deviating the grains from the concentric circles.
While in the prior art magnetic disk the adsorption is improved by reducing the area of contact between the magnetic head and magnetic disk through randomization of the direction of the polishing grains on the substrate surface by causing slight deviation of the grains from the concentric circles, there is a limit on the reduction of the contact area by such method. Therefore, in order to prevent the adsorption of the magnetic head, it is necessary to increase considerably the surface roughness of the substrate (i.e., the depth of the polishing nodes). Increasing the surface roughness of the substrate leads to the possibility of error generation when the information is read out from the magnetic disk or the reduction of the durability of the magnetic disk.
In the U.S. Pat. No. 5,134,038, there is disclosed a magnetic storage medium composed a non-wet-table substrate upon which a transient liquid metal layer is deposited and maintained as a distribution of discontinuous liquid features. However, to obtain the magnetic storage medium it is required to melt the metal at high temperature and sometimes to process the material under the vacuum condition.